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Cobalt oxides are known for their excellent heat transfer properties. The main component of cobalt oxides is the CoO2 monolayer, which exhibits high-temperature superconductivity caused by strong electron–phonon coupling (EPC). We here systematically investigate the structural stability, electronic structure, and magnetism of the CoO2 monolayer using first-principles and Monte Carlo simulations. On this basis, we further study the changes in the spin energy gap, magnetic axis direction, and other properties of the CoO2 monolayer with the changes in carrier concentration. By appropriately doping the CoO2 monolayer with holes, the magnetic axis direction of the CoO2 monolayer can be reversed, thereby enhancing its potential application in the field of spin electronic devices. Monte Carlo simulation is used to study the regulation of different factors on the magnetothermal properties of the CoO2 monolayer. Through the analysis of physical parameters such as Curie temperature (TC) and bandgap, we find that the appropriate carrier concentration and magnetic field can not only regulate the magnetothermal properties of materials but also further improve the efficiency of materials in low-temperature environments. [ABSTRACT FROM AUTHOR]

Magnetic nanocomposite was prepared using the wet chemical precipitation approach with varying amounts of cobaltous oxide (CoO). The concentrations of CoO were 0.5, 3.5, 6.5, and 9.5 g per 100 % wollastonite composition. Samples were sintered separately at 1000 and 1200 °C. X-ray diffraction analysis (XRD) of the sintered parent sample revealed the formation of wollastonite CaSiO 3 and larnite Ca 2 SiO 4 , as well as a minor silicon oxide SiO 2 phase. In CoO-doped samples, Co-åkermanite Ca 2 CoSi 2 O 7 and other phases were formed. The XRD and scanning electron microscope SEM confirm the samples' submicron and nanocrystalline microstructure. The Fourier transform infrared spectroscopy (FTIR) and Raman spectra (RS) of investigated samples sintered at 1000 and 1200 °C revealed their bond structure. Both analyses confirmed that incorporating CoO into CaSiO 3 significantly improved its vibrational modes, reflecting structural modifications. By increasing the cobalt oxide content from 3.5 to 9.5 wt%, the samples attain the ideal paramagnetic state, as demonstrated by the magnetic hysteresis (M − H) curve, which is linearly reversible. Formation of the Ca 2 CoSi 2 O 7 significantly alters the magnetic characteristics of the samples, whether through increasing the cobalt oxide concentration up to 9.5 wt% or modifying the sintering temperature. This enables the prepared nonocomposites to be suitable for novel magnetic applications. [ABSTRACT FROM AUTHOR]

Herein, we present a quick and cost-effective electrodeposition method to synthesize binder-free cobalt oxide (Co3O4) nanostructures. The structural crystallinity of the prepared electrodes was examined using X-ray diffraction (XRD), while Fourier-transform infrared spectroscopy (FTIR) was used to study the stretching and bending vibrations of metal–oxygen bonds. Scanning electron microscopy (SEM) revealed that as the concentration increased from 1 mM, nanoparticles transitioned from agglomeration to sheet formation. The supercapacitor properties of these Co3O4 nanostructure electrodes were investigated in a 6 M KOH solution. Among the electrodes, Co3O4@FNF-1 exhibited the highest capacitance of 1444 F g−1 at a current density of 0.5 A g−1. Additionally, the optimized Co3O4@FNF-1 electrode demonstrated 96% stability after 8000 cycles and showed excellent glucose sensing capabilities. These findings suggest that the binder-free Co3O4 electrode is a promising candidate for high-performance supercapacitor and biosensing applications. [ABSTRACT FROM AUTHOR]

Rechargeable sodium‐ion batteries are promising sustainable energy storage systems, owing to their low cost and high energy density. However, the existing cathode chemistries, particularly layered sodium transition metal oxides, exhibit restricted electrochemical performance, which hinders their extensive applications. To overcome challenges, originating from kinetically limited structural transformations, various cation substitutions are reported in the literature. Especially the partial Na–K replacement is discussed recently, which can increase bulk Na‐diffusivity and suppress undesirable phase transitions. Here, a critical study of potassium doping in different layered materials P3‐K0.5Co0.33Mn0.67O2 and P3‐K0.5Co0.33Mn0.67O2*0.5H2O with redox‐active Co (and Mn), and P2‐Na0.7Co0.8Ti0.2O2 and P2‐K0.1Na0.7Co0.8Ti0.2O2 with Co activity is presented. It is found that the presence of K significantly enhances the moisture sensitivity: P3‐K0.5Co0.33Mn0.67O2*0.5H2O is quickly formed in the air from K0.5Co0.33Mn0.67O2, while Na0.7Co0.8Ti0.2O2 remains stable under the same conditions. In electrochemical Na‐cells, a partial K–Na cation exchange in P3‐K0.5Co0.33Mn0.67O2 and P3‐K0.5Co0.33Mn0.67O2*0.5H2O occurs without applying current. The electrochemical performance of P3‐K0.5Co0.33Mn0.67O2 is slightly increased in comparison to K‐free P2‐Na0.67Co0.33MnO.67O2 from the literature, staying, however, behind the performance of Na0.7Co0.8Ti0.2O2. K0.1Na0.7Co0.8Ti0.2O2 shows weaker rate capability than isostructural Na0.7Co0.8Ti0.2O2, reflecting a negative impact of K on Na‐diffusivity. Therefore, effect of K‐incorporation in layered structures on the battery performance strongly depends on the cathode composition. [ABSTRACT FROM AUTHOR]

The spinel-type cobalt oxide decorated halloysite nanotubes (HNTs), Co 3 O 4 /HNTs and Co 1-x Al x (Co x Al 2-x)O 4 /HNTs hybrid catalysts were fabricated via a facile two-step process: synthesis of Co-MOF/HNTs composites, followed by annealing treatment at 300–900 °C for 2 h. The novel catalysts can be used to efficiently activate peroxymonosulfate (PMS) degrade of the refractory pollutant norfloxacin (NOR) in aqueous solution. Additionally, the adsorption process of the HNTs enhanced the elimination performance of NOR by the catalysts. We investigated how annealing temperature affected the crystalline structure and cation distributions of Co2+ and Al3+ occupying tetrahedral and octahedral interstices of the oxygen sub-lattice. The results exhibited that two types of spinel reconstructions, namely Co 3 O 4 and CoAl 2 O 4 , fixed on HNTs existed in temperature ranging of 300–600 °C and above 900 °C, respectively. However is the presence of composite spinel Co 1-x Al x (Co x Al 2-x)O 4 was present at 700–800 °C. The study also revealed that precursor thermal behavior significantly influenced the activity, ion leaching, metal coordination structures, and oxygen coordination structures of the catalysts. The simultaneous generation of oxygen vacancies during the doping of Al changes the inherent electronic structure of the oxide, resulting in a lower coordination number of Co and the presence of more dangling bonds on the surface, and the Co2+ near the oxygen vacancies will preferentially adsorb the active oxide, promoting the transfer of electrons on the catalyst surface. The present study provides insights into constructing modified mineral material catalysts with enhanced catalysis and adsorption capabilities as promising solutions for peroxymonosulfate purification applications targeting multi-antibiotic contaminants. [ABSTRACT FROM AUTHOR]

This research aims to elucidate the intricate electrical and thermal characteristics of lithium-ion batteries under varying electrode types, encompassing Lithium Iron Phosphate (LFP), Lithium Nickel Manganese Cobalt Oxide (NMC), and Lithium Nickel Cobalt Aluminium Oxide (NCA). The experimental investigations were meticulously conducted employing two distinct methodologies: constant current discharge and pulse current discharge. Furthermore, a novel modeling technique was introduced, entailing the utilization of an electrical equivalent circuit model. The findings of this study reveal a complex, non-linear correlation between the quantity of charge and the open-circuit voltage (OCV) throughout the discharge progression. It was observed that the State of Charge (SOC), OCV, and terminal voltage (Vt) undergo alterations in a synchronous manner, albeit in a non-linear fashion. Particularly noteworthy is the observation that the LFP demonstrated a comparatively minimal fluctuation in voltage when juxtaposed with the NMC and NCA, all at changing of equivalent SOC levels. The generation of heat remained relatively uniform throughout the discharge process, exhibiting escalated rates when the SOC levels plummeted below 0.2 or escalated beyond 0.8. Regarding the electrodes, it is notable that the NMC variant showcased the highest rate of heat generation, with NCA and LFP in close succession. In the chapter concerning modeling, the suggested model demonstrated a noteworthy level of precision in predicting Vt values for SOC within the range of 1.0 to 0.2. The mean error margin was determined to be 0.004404 V, equivalent to 1.176% for NMC, -0.0256 V, corresponding to 1.126% for NCA, and -0.07 V, representing 2.601% for LFP. [ABSTRACT FROM AUTHOR]

Doping and compositing are two universal design strategies used to engineer the electronic state of a material and mitigate its disadvantages. These two strategies are extensively applied to design efficient electrocatalysts for water splitting. Using cobalt oxide (CoO) as a model catalyst, it is proven that the oxygen evolution reaction (OER) performance can be progressively improved, first by Fe‐doping to form Fe‐CoO solid solution, and further by the addition of CeO2 to produce a Fe‐CoO/CeO2 composite. X‐ray absorption spectroscopy (XAS) reveals that distinct electronic interactions are induced by the processes of doping and compositing. Fe‐doping of CoO can break down the structural symmetry, changing the electronic structure of both Co and O species at the surface and decreasing the flat‐band potential (Vfb). In comparison, subsequent compositing of Fe‐CoO with CeO2 induces negligible electronic changes in the Fe‐CoO (as seen in ex situ characterizations), but significantly modifies the oxidative transformations of both Co and Fe under OER conditions. The spectroscopic investigations reveal that Fe‐doping and CeO2 compositing play different roles in modifying the electronic properties of CoO in its pristine state and during OER catalysis, in return, providing useful guidance for the design of more efficient electrocatalysts using these two strategies. [ABSTRACT FROM AUTHOR]

Lanthanum Strontium Cobalt Ferrite Oxide (LaSrCoFeO 3) has been widely used as cathode material for intermediate-temperature solid oxide fuel cells at the temperature of 500–800 °C. At this temperature range, understanding the electrochemical behavior which is commonly analyzed by complex nonlinear least-squares (CNLS) analysis is very crucial in improving the cathode's performance. However, this analysis shows some limitations in interpreting the electrochemical processes in detail, particularly at the electrode-electrolyte interface. Hence, this study is conducted to compare the electrochemical impedance data analyses by CNLS and the distribution of relaxation times (DRT) of a fabricated LaSrCoFe|BCZY|LaSrCoFe (LaSrCoFe La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 and BCZY=BaCe 0.54 Zr 0.36 Y 0.1 O 2.95) symmetrical cell. Impedance data of the cell is collected at T = 800 °C at two different stabilization times and to further enhance the analysis process, the impedance data of the cell at measurement temperatures of 700 °C and 750 °C are also included. In a Nyquist plot, the cell exhibits depressed semi-circles that represent a few processes occurring at the interface. The DRT analysis is more precise and easily reveals the semi-circles consisting of four different sub-processes (represented by four peaks) than CNLS (represented by four impedance arcs). The extracted responses from both analyses correspond to the oxygen reduction reactions that follow the Adler-Lane-Steele model. The stabilized symmetrical cells for respective 34 h and 17 h show an area-specific resistance (ASR) of (i) 0.22 Ωcm2 and 0.30 Ωcm2 (by CNLS) and (ii) 0.20 Ωcm2 and 0.26 Ωcm2 (by DRT). In addition, the ASR of the cell at T = 700 °C and T = 750 °C after being stabilized for 34 h is (iii) 0.71 Ωcm2 and 0.40 Ωcm2 (by CNLS) and (iv) 0.70 Ωcm2 and 0.44 Ωcm2 (by DRT), accordingly. Conversely, the cell's microstructure is not affected by the applied stabilization periods as observed by a scanning electron microscope. [Display omitted] • DRT analysis predominantly expresses P 1 , P 2 , P 3 and P 4 cathode sub-processes. • The 34 h stabilization period is sufficient to stabilize a 25-mm PCFC button cell. • ASR value of the S34 is lower than S17 according to DRT and CNLS analysis. • Shorter relaxation time means a faster kinetic reaction of electrochemical processes. [ABSTRACT FROM AUTHOR]

Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ (BSCF) generally exhibits superior cathode activity compared to La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ (LSCF) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, the chemical stability of BSCF is inferior to that of LSCF. When BSCF cathodes are sintered at a high temperature of 1050 °C, performance was compromised due to the formation of (Ba,Sr)ZrO 3 between the scandia-stabilized zirconia (ScSZ) electrolyte and gadolinia-doped ceria (GDC) interlayer. The oxide ionic conductivity of (Ba,Sr)ZrO 3 was low, decreasing the cathode performance. Furthermore, the BSCF grains enlarged, and cobalt oxide formed due to BSCF decomposition, decreasing the active specific surface area. However, by incorporating GDC into the BSCF cathode, the morphology remained unchanged and cobalt oxide formation was prevented, despite (Ba,Sr)ZrO 3 still forming. The performance of the cell with the BSCF-GDC composite cathode surpassed that with the BSCF cathode due to decreased polarization resistance attributed to the oxygen surface exchange and diffusion processes in the cathode. [ABSTRACT FROM AUTHOR]

In this work we developed a hydrothermal method for synthesizing amorphous Ni−Co hydroxide (NC(OH)) and in the subsequent step crystalline NiCo2O4 (NCO) has been produced using water as the solvent. For nickel‐zinc batteries, NC(OH) was found to have superior performance to its NCO prepared by two‐step process. The thermal stability analysis exhibited the optimum temperature to obtain the NC(OH), and NCO electrode materials. The XRD pattern showed mixed phases containing both Ni and Co hydroxides (during the initial step) and in the subsequent step (calcined) the formation of cubic spinel structure was noticed. For NC(OH), aggregated particles with irregular morphology were observed while clustered nanorod‐like shapes were noticed for NCO samples. To be noted, that the nanorod morphology was obtained through a facile approach without employing any structure‐directing agent. Both NC(OH) and NCO were employed as cathodes for Ni−Zn battery studies against Zn foil anode with a polyamide‐based separator soaked in 6 M KOH saturated with ZnO additive was used as electrolyte. The Ni−Zn cell was fabricated in CR2032 coin cell configuration. The electrochemical studies such as cyclic voltammetry (CV) showed the characteristic redox peaks for NC(OH) sample exhibiting high peak current compared to its NCO counterpart. The NC(OH) had a capacity of 268 mAh g−1 against 120 mAh g−1 for NCO at a current density of 1 Ag−1. The cell was able to retain 85 % of the capacity at the end of 500 cycles and showed remarkable rate capability. The Ni−Zn battery presents energy and power densities of 428.8 Wh Kg−1 and 2.68 kW Kg−1, respectively surpassing the normal values reported for aqueous rechargeable batteries. Owing to the presence of Ni and Co in hydroxide form (reduced crystallinity) the NC(OH) sample showed improved electrochemical activity. This work provides a facile approach and effective strategy for developing bimetallic hydroxides for optimal energy storage performance. [ABSTRACT FROM AUTHOR]

This study investigates the effect of thermal treatment on the composition and morphology of cobalt oxide nanofibers synthesized via electrospinning. Cobalt acetate tetrahydrate and poly (vinyl alcohol) were used as precursors to produce cobalt acetate/poly(vinyl alcohol) nanofiber mats. The electrospun mats were subjected to various thermal treatments, including calcination in air at 500∘C, calcination under argon at 700∘C and 850∘C and treatment with water gas (CO and H2) at 180∘C. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were employed to characterize the nanofibers. The results demonstrated that the polycondensation tendency of cobalt acetate and the supportive properties of poly(vinyl alcohol) led to the maintenance of nanofibrous morphology across all thermal treatments. Calcination in air produced dense, highly crystalline Co3O4 nanofibers. In contrast, calcination under argon at 700∘C resulted in an amorphous carbon matrix embedded with small cobalt-based nanoparticles, while at 850∘C, the nanofibers contained larger, highly crystalline cobalt nanoparticles. Thermal treatment with water gas transformed the nanofibers into nano-belts primarily composed of crystalline CoO and Co3O4, with minimal amorphous phase. This study highlights the critical influence of thermal treatment on the structural and compositional properties of cobalt-based nanofibers, offering insights for tailoring these materials for applications in catalysis, energy storage and electronic devices. The findings emphasize the potential of controlled thermal strategies to produce diverse cobalt-based nanostructures with distinct properties. [ABSTRACT FROM AUTHOR]

The present study reports the synthesis, characterization, and application of NiCo bimetallic catalysts to produce 2,5‐furandicarboxylic acid (FDCA) via the oxidation of bio‐renewable 5‐hydroxymethylfurfural (HMF). FDCA is a biopolymer precursor and a potential replacement for terephthalic acid (TPA). The catalysts were synthesized via the co‐precipitation method in different molar ratios of NiCo, followed by calcination in a muffle furnace. As a result, the complete conversion of HMF and a maximum 84.89 % FDCA yield was measured at 50 °C in 50 minutes in the presence of NiCo(3 : 1) catalyst. In addition, effect reaction parameters, including catalyst amount, temperature, time, base, and oxidant amount on the FDCA yield, were studied, and the process was optimized. The NiCo(3 : 1) catalyst showed a negligible loss in activity for at least five cycles. The higher catalytic activity and stability are attributed to the synergistic effect of bimetallic catalysts, such as higher lattice oxygen. Accordingly, the catalyst was characterized using BET, XRD, H2‐TPR, CO2‐TPD, HR‐TEM, and XPS to correlate their properties and activity. The reaction products were analyzed quantitatively using HPLC and qualitatively using HR‐MS. [ABSTRACT FROM AUTHOR]

This review article focuses on the potential of cobalt oxide composites with conducting polymers, particularly polypyrrole (PPy) and polyaniline (PANI), as advanced electrode materials for supercapacitors, batteries, and supercapatteries. Cobalt oxide, known for its high theoretical capacitance, is limited by poor conductivity and structural degradation during cycling. However, the integration of PPy and PANI has been proven to enhance the electrochemical performance through improved conductivity, increased pseudocapacitive effects, and enhanced structural integrity. This synergistic combination facilitates efficient charge transport and ion diffusion, resulting in improved cycling stability and energy storage capacity. Despite significant progress in synthesis techniques and composite design, challenges such as maintaining structural stability during prolonged cycling and scalability for mass production remain. This review highlights the synthesis methods, latest advancements, and electrochemical performance in cobalt oxide/PPy and cobalt oxide/PANI composites, emphasizing their potential to contribute to the development of next-generation energy storage devices. Further exploration into their application, especially in battery systems, is necessary to fully harness their capabilities and meet the increasing demands of energy storage technologies. [ABSTRACT FROM AUTHOR]

The lifespan of lithium (Li) metal batteries (LMBs) can be greatly improved by the formation of inorganic‐rich electrode‐electrolyte interphases (EEIs) (including solid‐electrolyte interphase on anode and cathode‐electrolyte interphase on cathode). In this work, a localized high‐concentration electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI) salt, 1,2‐dimethoxyethane (DME) solvent and 1,2‐bis(1,1,2,2‐tetrafluoroethoxy)ethane (BTFEE) diluent is optimized. BTFEE is a fluorinated ether with weakly‐solvating ability for LiFSI so it also acts as a co‐solvent in this electrolyte. It can facilitate anion decomposition at electrode surfaces and promote the formation of more inorganic‐rich EEI layers. With an optimized molar ratio of LiFSI:DME:BTFEE = 1:1.15:3, LMBs with a high loading (4 mAh cm−2) lithium nickel manganese cobalt oxide (LiNi0.8 Mn0.1 Co0.1) cathode can retain 80% capacity in 470 cycles when cycled in a voltage range of 2.8–4.4 V. The fundamental understanding on the functionality of BTFEE revealed in this work provides new perspectives on the design of practical high‐energy density battery systems. [ABSTRACT FROM AUTHOR]

The effect of the support in the incorporation of cobalt oxide nanoparticles on mesoporous materials (SBA‐15) and mesoporous cellular foam (MCF) was investigated. The materials were characterized using various techniques. The XRD diffraction patterns showed that the porous structures remained after cobalt incorporation, while high‐angle XRD of the MCF showed CoO peaks, in contrast to Co‐SBA‐15 which exhibited Co3O4. This was confirmed by XPS technique. The SEM‐EDS and HRTEM‐STEM microscopy indicate a distribution of cobalt oxides uniform in the samples synthesized and the average size of the particles is 1.88 nm. H2‐TPR analysis highlighted the interaction between the support surfaces and the metal oxide (SMSI). It was observed that in the SBA‐15 structure, small clusters of cobalt oxide formed with a strong interaction with silica, leading to high reduction temperatures. The catalysts activity was characterized in oxidation reactions of Methyl Phenyl Sulfide and a correlation was observed between the characterization results and the enhanced selectivity and yield towards sulfone exhibited by Co‐MCF. [ABSTRACT FROM AUTHOR]

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Reasonable design of low‐cost, high‐efficiency and stable bifunctional oxygen electrocatalysts is of great significance to improve the reaction efficiency of Zn‐air batteries, which is still a huge challenge. Here, we report a highly efficient bifunctional oxygen electrocatalyst with three‐dimensional (3D) N‐doped graphene network‐supported cobalt and cobalt oxide nanoparticles (Co/CoO‐NG), which can be in situ synthesized by inducing metal ions on metal plates via graphene oxide as an inducer. This 3D network structure and open active center show excellent bifunctional oxygen electrocatalytic activity under alkaline conditions, and can be used as an air electrode in rechargeable Zn‐air batteries, with significantly better power density (244.28 mW cm−2) and stability (over 340 h) than commercial Pt/C+RuO2 mixtures. This work is conducive to advancing the practical application of graphene‐based materials as air electrodes for rechargeable zinc‐air batteries. [ABSTRACT FROM AUTHOR]

For the first time, the dominant magnetoelectric activity of ZIF-67-derived carbonaceous microparticles embedded with Co nanoparticles and distinctive magnetothermal effect of MIL-88B-derived Fe3O4 nanocubes decorated on carbonaceous microrods, respectively, were explored to be controlled by the structure of the MOF-derived electrically conductive carbonaceous matrix and metal nanoparticles. [ABSTRACT FROM AUTHOR]

AbstractIn this study, the impact of cobalt iron oxide(CoFe2O4) on the anaerobic digestion (AD) of food waste (FW) was investigated including the variations in pH, VFAs, ORP, Fe2+/Fe3+ concentrations, SCOD, dehydrogenase activity, methane production and microbial community structure. The results showed that CoFe2O4 had a positive effect on the anaerobic digestion of food waste. CoFe2O4 could promote the release of SCOD, increase the dehydrogenase concentration and reduce ORP resulting in an increase of methane production. At a CoFe2O4 concentration of 200 mg/L, the cumulative methane production reached to 414.75 mL/(gVS) which was increased by 79.1% compared to the control group(231.59 mL/(gVS)). Meanwhile, the variation of microbial community showed that CoFe2O4 could increase the relative abundance of Methanobacterium and the methane production pathway in the AD was shifted from acetoclastic to hydrogenotrophic. [ABSTRACT FROM AUTHOR]

Transition metal oxides have been widely used in microwave-absorbing materials, but how to improve impedance matching is still an urgent problem. Therefore, we introduced urea as a polymer carbon source into a three-dimensional porous structure modified by Co3O4 nanoparticles and explored the influence of different heat treatment temperatures on the wave absorption properties of the composite. The nanomaterials, when calcined at a temperature of 450 °C, exhibited excellent microwave absorption capabilities. Specifically, at an optimized thickness of 9 mm, they achieved a minimum reflection loss (RLmin) of −97.3 dB, accompanied by an effective absorption bandwidth (EAB) of 9.83 GHz that comprehensively covered both the S and Ku frequency bands. On the other hand, with a thickness of 3 mm, the RLmin was recorded as −17.9 dB, with an EAB of 5.53 GHz. This excellent performance is attributed to the multi-facial polarization and multiple reflections induced by the magnetic loss capability of Co3O4 nanoparticles, the electrical conductivity of C, and the unique three-dimensional structure of diatomite. For the future development of bio-based microwave absorption, this work provides a methodology and strategy. [ABSTRACT FROM AUTHOR]

Crystal violet dye poses significant health risks to humans, including carcinogenic and mutagenic effects, as well as environmental hazards due to its persistence and toxicity in aquatic ecosystems. This study focuses on the efficient removal of crystal violet dye from aqueous media using novel Co3O4/Co3(BO3)2 nanostructures synthesized via the Pechini sol–gel approach. The nanostructures, which were abbreviated to EN600 and EN800, were fabricated at calcination temperatures of 600 and 800 °C, respectively. X-ray diffraction (XRD) analysis revealed that the synthesized samples have a cubic Co3O4 phase and an orthorhombic Co3(BO3)2 phase, with mean crystal sizes of 43.82 nm and 52.93 nm for EN600 and EN800 samples, respectively. The Brunauer–Emmett–Teller (BET) surface areas of EN600 and EN800 samples were 65.80 and 43.76 m2/g, respectively, indicating a significant surface area available for adsorption. Optimal removal of crystal violet dye was achieved at a temperature of 298 K, a contact time of 70 min, and a pH of 10. The maximum adsorption capacities were found to be 284.09 mg/g for EN600 and 256.41 mg/g for EN800, which are notably higher compared to many conventional adsorbents. The adsorption process followed the pseudo-second-order kinetic model and fitted well with the Langmuir isotherm. The adsorption was exothermic, spontaneous, and physical in nature. Moreover, the adsorbents exhibited excellent reusability, retaining high efficiency after multiple regeneration cycles using 6 mol/L hydrochloric acid. These findings highlight the potential of these Co3O4/Co3(BO3)2 nanostructures as effective and sustainable materials for water purification applications. [ABSTRACT FROM AUTHOR]

Developing efficient bifunctional oxygen electrocatalysts is crucial for enhancing the performance of rechargeable Zn‐air batteries (ZABs). In this study, cobalt/cobalt oxides embedded in N‐doped carbon nanofibers (Co/CoOx/NCNFs) were synthesized through a combination of electrospinning and annealing processes. The resulting Co/CoOx/NCNFs catalysts feature abundant CoNx and CoOx active species, leveraging the large specific surface area of nanofibers to facilitate oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The optimized Co/CoOx/NCNFs‐0.1 achieved a half‐wave potential (vs. RHE) of 0.82 V and required only 429 mV to reach 10 mA cm−2 in a typical three‐electrode system with 0.1 M KOH using an electrochemical workstation equipped with a pine instruments rotator, outperforming the Pt/C+RuO2. The assembled ZABs exhibited high specific capacity (771 mAh gZn−1), substantial power density (981.6 mWh gZn−1), and long‐term stability (>325 h). In situ Raman spectroscopy confirmed that the electrocatalytic processes involve the redox activity of Co (II and III) species derived from abundant CoNx and CoOx, elaborating the origin of the catalysts’ exceptional oxygen electrocatalysis performance. This work not only presents a straightforward and effective approach for producing bifunctional oxygen electrocatalysts in ZABs but also sheds light on the catalytic mechanisms underlying ORR and OER for CoNx/CoOx‐based oxygen electrocatalysts. [ABSTRACT FROM AUTHOR]

Today, the rise of opportunistic infections and their resistance to current antifungal drugs has led to the inevitable need to produce effective antimicrobials at a reasonable cost. This study aimed at producing a calcium carbonate/cobalt oxide nanocomposite with the most excellent antifungal activity against Candida albicans (C. albicans). Thus, nine experimental designs using the Taguchi technique were utilized to discover the greatest combination of parameters for antifungal activity. The colony‐forming unit (CFU) method was used to test the produced nanocomposites' antifungal properties against C. albicans. The results indicated that the synthesized nanocomposite in optimal conditions (20 mg/mL of calcium carbonate, 3 mg/mL of cobalt oxide, and 90 min of stirring time) could inhibit the growth of C. albicans by more than 74%. Various analyses were applied to determine the structural properties of the calcium carbonate/cobalt oxide nanocomposite, and its constituents revealed the fabricated nanocomposite's desirable properties. In the study, the nanocomposite was an efficient antifungal agent that might be employed in various fields, including medicine, dentistry, and life sciences. [ABSTRACT FROM AUTHOR]

Under the gravity of future socio-economic development, the viability of water electrolysis still hinges on the accessibility of stable earth-abundant electrocatalysts and net energy efficiency. This work emphasizes the design and synthesis of two newly developed cobalt(II) complexes, [Co(HL)2(NCS)2] (Comono) and [Co2(L)3(CH3OH)]ClO4 (Codi), with a (N,O)-donor ligand, HL (2-methoxy-6-(((2-methoxyphenyl)imino)methyl)phenol). The study delves into understanding their structural, morphological, magnetic, and charge transport characteristics. Moreover, the study explores the potential of these complexes in catalyzing hydrogen production through heterogeneous electrocatalysis. The X-ray crystal structure of Comono reveals the octahedral geometry of the Co(II) ion, adopting two HL units and two NCS− units. The Codi complex exhibits a doubly-phenoxo-O-bridged (μ1,1) dinuclear complex, forming a typical octahedral geometry for both the Co(II) centres in coupling with three units of L−. Temperature-dependent magnetic susceptibility measurements showed that all of the Co(II) ion in Comono shows a typical paramagnetic behaviour for high spin octahedral Co(II) ions while the Co(II) centres in Codi are coupled with doubly-phenoxo-bridges bearing weak ferromagnetic characteristics at low temperature. Electron transport properties of the Co(II) complex-mediated Schottky device address the superior carrier mobility (μ) for Codi (9.21 × 10−5) over Comono (2.02 × 10−5 m2 v−1 s−1) with respective transit times of 1.70 × 10−9 and 7.77 × 10−9 s. Additionally, electron impedance spectral analysis supports the lower electrical transport resistance of Codi relative to Comono. The heterogeneous electrocatalytic HER activity of Codi and Comono in 0.1 M KOH shows excellent electrocatalytic efficiency in terms of the various electrochemical parameters. Constant potential electrolysis, multi-cycle CVs, and post-HER analysis reveal the pre-catalytic nature of the complexes, which in turn delivers Co3O4 nanoparticles as the active catalysts for efficient hydrogen evolution. [ABSTRACT FROM AUTHOR]

Facile sintering of metal oxides and ceramics is essential for energy-efficient manufacturing processes of various engineering systems. It should satisfy the increasing density of the resulting layer packed on the substrate in a mild environment and improve the specific performance through structural changes in the internal grain boundaries. However, conventional sintering inevitably involves maintaining high-temperature conditions for a long duration, resulting in energy inefficiency and unintended element diffusion. Herein, we report a novel composite-fuel-assisted sintering strategy as an alternative to conventional sintering for enhanced densification of manganese cobalt oxide (MCO) spinel. MCO spinels, which are commonly used to form a protective layer for metallic interconnects, are electrophoretically deposited on Cr-containing stainless steel, while the initial porosity and thickness are controlled by regulating the deposition parameters. Then, 2,4,6-trinitrophenol combined with sodium azide as a composite fuel is dropped onto the pre-deposited MCO layer. During air drying, this composite fuel tends to self-assemble into an elongated microwire-shaped structure featuring π-stacked aromatic rings and provides a serial connection between the dried fuel particles, facilitating their penetration into the coated material. The composite fuel enables the implementation of a combustion wave passing through the MCO layer in a mild sintering environment, thereby providing instantaneous thermal energy for densifying the initial MCO layer. The densification efficiency achieved using the optimized composite-fuel-assisted sintering strategy is 93 % higher than that achieved conventional air sintering. This study will pave the way for the development of new hybrid sintering strategies based on versatile composite fuels to achieve high efficiencies under mild environments. [ABSTRACT FROM AUTHOR]

COVID‐19 the most devastating pandemic of the current millennium, can survive from hours to months in environment, devices, and surface. Its transmission by asymptomatic carriers has significantly strained the existing testing resources. At present, there are no clinically proven therapeutic methods that effectively inhibit the effects of this virus. Nanoparticles (NPs) have been extensively utilized in various medical applications, including biosensing, drug delivery, imaging, and antimicrobial/antiviral treatment. Synthetic NPs can closely resemble the virus and strongly interact with its proteins due to their similar morphology. Therefore, NP‐based strategies for combating this virus hold immense potential and may reduce the survivability of the virus in the environment due to unique physicochemical features and surface modification properties. In this study, antiviral properties of silver (Ag), copper oxide (CuO), cobalt oxide (Co3O4), and cerium oxide (CeO2) NPs besides Ag and Cu sheets against COVID‐19 in nasopharyngeal samples were investigated. All NPs suspensions were prepared in Virus Transporter Media (VTM) in 25, 50, and 100 mg/mL concentrations, additionally, Cu and Ag sheets were added to SARS‐CoV‐2 virus pooled and then incubated at room temperature. Viral RNA was extracted from those suspensions after different incubation times and concentrations and quantitative polymerase chain reaction (qPCR) analysis was performed. For virucidal activity evaluation, the estimated lysed virus copy number was assessed according to the pooled virus sample serial dilution and eventually based on changes in the cycle threshold (CT) of qPCR. According to CT number changing after incubation of NPs with pooled virus sample, CuO NPs had the greatest virus inactivation on virus lysis at all concentrations and times while Co3O4 NPs showed moderate antiviral activity (P<0.05). The antiviral activity of other NPs was less than CuO and Co3O4 and were almost identical at similar concentrations and times. Cu and Ag sheets have shown a direct linear relationship between incubation time and antiviral activity. Cu nanoparticles had significant destructive effects on the SARS‐CoV‐2 virus among all nanoparticles, and the Cu sheet had considerably less antiviral activity than its own Cu NPs. These findings might make it helpful to use CuO NPs in masks, and air/water filters, make coated surfaces with effective NPs, and manufacture disinfectant solutions to combat coronaviruses and other viruses that can cause respiratory infections. [ABSTRACT FROM AUTHOR]

Zinc cobalt oxide nanostructures were synthesized by electrochemical deposition of zinccobalt alloy at various bath temperatures (15, 30, 45 and 60 °C) and its hydrothermal oxidation at 100 °C. X-ray diffraction pattern and Raman spectroscopy data reveals the formation of spinal structure of ZnCo2O4. Photoluminescence spectra of the samples exhibit broad peaks with a red shift in the emission energy. Diffused reflectance spectroscopy measured the band gap of the synthesized materials; band gap is 3.06, 3.03, 3.02 and 2.99 eV, for samples electrodeposited at 15, 30, 45 and 60 °C, respectively. Optical conductivity of synthesized materials decreases with increasing deposition layers while reflectance shows opposite trend. Thermoelectric set up measures the change in potential difference through synthesized materials when different temperatures are applied and an increment in potential were observed. Seebeck co-efficient and power factor are also studied as function of bath temperature. [ABSTRACT FROM AUTHOR]

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H2 reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H2 to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H2/CO = 2.0, gas hourly space velocity (GHSV) 510 h–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C5+ products (64 vs. 54%) and lower selectivity for CH4 (11 vs. 17%), CO2 (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C5+ productivity measured as g C5+ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment. [ABSTRACT FROM AUTHOR]

Ternary nanocomposites of reduced graphene oxide/multi-walled carbon nanotubes/cobalt oxide nanoparticles (rGO/MWCNT/Co3O4) were synthesized employing a facile hydrolysis method with subsequent heat treatment. The good electrical conductivity and remarkable carrier mobility of rGO and MWCNTs make them a suitable matrix for hybrid supercapacitors, and their composites with metal oxides exhibit enhanced electrochemical properties due to the advantages of the synergistic contribution and the integration of different dimensionalities. The binary counterparts of Co3O4 with GO or MWCNTs were also produced using the same technique to gain additional insight into the characteristics of the individual components. The structural and morphological properties of the composites were analyzed using various analytical techniques. The electrochemical behaviors of the prepared composites were investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4. A platinum electrode modified with the rGO/MWCNT/Co3O4 composite displayed a remarkable specific capacitance of 922 F g−1 at a current density of 1 A g−1 composite with a negligible capacitance drop after 2000 cycles. The symmetric supercapacitor fabricated using the rGO/MWCNT/Co3O4 composite showed an energy density of 32.2 Wh Kg−1 at 1 A g−1, and the corresponding power density was 2000 W Kg−1. The supercapacitor fabricated using the composite displayed 83% capacitance retention after 2000 cycles at 3 A g−1 composite. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Education & Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work reports the solution combustion synthesis of negatively charged cobalt oxide nanoparticles (CONPs) using glycine as a fuel. The morphology, composition, crystallinity, and surface characteristics of synthesized CONPs were confirmed. The particles were oval in shape with an average size of 10 ± 2 nm and negatively charged functional groups (C-H and N = N = N) on their surface. Batch experiments were performed to estimate the optimum values of parameter to estimate the maximum Cu(II) adsorption of CONPs, which was found to be 523 ± 12.72 mg g−1. The acid treatment achieved regeneration of loaded CONPs, and their sustainability was checked by performing adsorption–desorption experiments up to 4 cycles. The obtained results showed only a 14.4% reduction in adsorption capacity up to 4 cycles. Further, the diversified application of CONPs was examined by exposing them to synthetically prepared textile industry effluent containing multiple metal ions. The batch study data were fitted to various isotherm and kinetic models to understand the adsorption kinetics. The possible mechanism for the adsorption of Cu(II) onto CONPs has also been discussed. The antimicrobial assay results advocated that the disposal of CONPs is harmless to the ecosystem. [ABSTRACT FROM AUTHOR]

Currently, interfacial solar steam generation (ISSG) in desalinating water has become very popular for obtaining purified water from polluted water. However, finding an efficient evaporator with low cost is a challenging task for researchers. In this work, we introduce natural bamboo wood (BW) that acts as an interfacial evaporator for obtaining purified water. Four different wood evaporators namely, flat wood (BW-FW), two-cut grooved wood (BW-2G), four-cut grooved wood (BW-4G), and four-cut grooved with Co3O4-coated wood (BW-4G/Co3O4) are used to study the mass loss (ML), evaporation rate (ER), and evaporation efficiency (EY). From the observations, BW-4G/Co3O4 gives an admirable ML, ER, and EY of 4.4 g, 3.366 kg m−2 h−1, and 91.34% under 1 sun illumination for 60 min. Also, the BW-4G/Co3O4 evaporator is kept under natural sun illumination. It achieves 17.8 g of ML, 1.92 kg m−2 h−1 of ER, and 76% of EY respectively under 604.762 W/m2 solar illumination for 8 h. The reasons for the observed results are as follows: (i) the presence of grooves increases the exposing area for solar illuminations, (ii) super hydrophilicity nature of wood gives continuous replenishment of water from the bottom to the evaporative surface, (iii) the excellent salt rejection property of wood aids in continuous water transportation without salt accumulations. As a result of the condensed seawater samples, the ion concentrations (zinc, magnesium, cadmium, lead, copper, and sodium) come under WHO standards. Consequently, it gives better dye water separation from polluted water. [ABSTRACT FROM AUTHOR]

The influence of cobalt and cobalt–manganese oxide coating thickness on its ability to be a good diffusion barrier against Cr outward diffusion was investigated for stainless steel interconnects (AISI 441) of a solid oxide cell (SOC). The coatings were all synthesized using a DLI-MOCVD (Direct Liquid Injection-Metal Oxide Chemical Vapor Deposition) hot wall reactor. The study shows that a minimum cobalt oxide thickness of 300 nm was needed to be a good diffusion barrier against Cr for the 500-h exposure test. This observation was linked to the Mn concentration reached in the cobalt spinel during exposure. Indeed, during exposure at high temperature, Mn diffused from the substrate into the cobalt coating and transformed cobalt spinel into Co-Mn spinel. Whereas pure cobalt spinel was a good Cr diffusion barrier, cobalt-manganese spinel, Co3-xMnxO4, was not when x > 2. The thickness of the cobalt coatings must be chosen so that the Mn quantity coming into it from diffusion from the substrate does not degrade the protectiveness of the coating. [ABSTRACT FROM AUTHOR]

The present work investigates electrochemical oxidation of chlorine using cobalt oxide (Co3O4) nanoparticles synthesized through a co-precipitation method, resulting in a cubic lattice structure with space group Fd-3m (227). This study demonstrates that Co3O4 nanoparticles exhibit superior performance compared to noble electrocatalysts in chlorine evolution reactions (CERs). Key electrocatalytic parameters were optimized, with Co3O4 achieving an overpotential of 120 mV at a current density of 10 mA cm−2, a Tafel slope of 112 mV d−1 and a charge transfer resistance of 9.6 Ω. Additionally, wettability results revealed that cobalt oxide possesses minimal hydrophobicity, which helps in faster chlorine evolution process. We believe, this study provides valuable addition in understanding the designing of effective electrocatalysts for CER. [ABSTRACT FROM AUTHOR]

[Display omitted] • A green and efficient microwave-assisted leaching is proposed for metal recovery. • Citric acid shows a superior performance as a reductant in leaching efficiency. • Nearly 100 % metals are recovered using 0.2 mol/L H 2 SO 4 and 0.05 mol/L citric acid. • Kinetic analysis is performed to understand microwave-assisted leaching process. The management and sustainable recycling of spent lithium-ion batteries (LIBs) holds critical importance from both economic and environmental standpoints. H 2 O 2 and ascorbic acid are widely used inorganic and organic reductants in the hydrometallurgical process for battery recycling. In this study, citric acid, as a reductant, was found to have superior metal leaching efficiencies under microwave-assisted leaching than H 2 O 2 and ascorbic acid. The enhanced performance was attributed not only to the inherent reducing property of citric acid but also to the chelation of citric acid with Cu and Fe, resulting in the formation of reductive radicals under microwave. The effect of acid type, H 2 SO 4 concentration, citric acid concentration, solid-liquid (S/L) ratio, reaction time, and temperature were investigated. 99.5 % of Li, 99.7 % of Mn, 99.5 % of Co, and 99.3 % of Ni were leached from spent lithium nickel manganese cobalt oxides (NCM) battery black mass using 0.2 mol/L H 2 SO 4 and 0.05 mol/L citric acid at 120 °C for 20 min with a fixed S/L ratio of 10 g/L in the microwave-assisted leaching process. Leaching kinetic results were best fitted with the Avrami model, suggesting that the microwave-assisted leaching process was controlled by diffusion. The leaching activation energies of Li, Mn, Co, and Ni were 30.11 kJ/mol, 27.48 kJ/mol, 21.32 kJ/mol, and 33.29 kJ/mol, respectively, providing additional evidence that supports the proposed diffusion-controlled microwave-assisted leaching mechanism. This method provided a green and efficient solution for spent LIBs recycling. [ABSTRACT FROM AUTHOR]

The simple and cost‐effective co‐precipitation method is used for the synthesis of pure Co3O4 and 5% Sn‐doped Co3O4 nanoflakes. Crystallographic parameters, chemical composition, morphological properties, optical properties, and surface area are analyzed using X‐ray diffraction data (XRD), Fourier transform infrared spectroscopy (FT‐IR), Raman analysis, UV–vis, field emission scanning microscopy, energy‐dispersive X‐ray analysis, and Brunauer–Emmett–Teller (BET), respectively. By using cyclic voltammetry and electrochemical impedance spectroscopy in a 2 m KOH electrolyte, the electrochemical characteristics of both pure and 5% Sn‐doped Co3O4 are verified. The sample results show that the presence of Sn2+ has an impact on surface area, band gap, specific capacitance, and electrochemical performance of Co3O4. According to XRD data, synthetic material has a cubic structure. The surface area of the sample is scrutinized using BET which exhibits a higher surface area of 1084.998 m2 g−1 than pure Co3O4 (92.842 m2 g−1) demonstrating that enhancement in surface area as dopant concentration increases. It is observed that porous 5% Sn‐doped Co3O4 nanoflakes has the higher specific capacitance, i.e., 203.6 F g−1 with a high surface area. It is well noticed that drastic change in specific capacitance with 5% Sn doping. These observations and experiments reveal that designed electrode is a promising candidate for supercapacitor application. [ABSTRACT FROM AUTHOR]

Nickel cobalt oxides (NCOs) are promising, non‐precious oxygen evolution reaction (OER) electrocatalysts. However, the stoichiometry‐dependent electrochemical behavior makes it crucial to understand the structure‐OER relationship. In this work, NCO thin film model systems are prepared using atomic layer deposition. In‐depth film characterization shows the phase transition from Ni‐rich rock‐salt films to Co‐rich spinel films. Electrochemical analysis in 1 m KOH reveals a synergistic effect between Co and Ni with optimal performance for the 30 at.% Co film after 500 CV cycles. Electrochemical activation correlates with film composition, specifically increasing activation is observed for more Ni‐rich films as its bulk transitions to the active (oxy)hydroxide phase. In parallel to this transition, the electrochemical surface area (ECSA) increases up to a factor 8. Using an original approach, the changes in ECSA are decoupled from intrinsic OER activity, leading to the conclusion that 70 at.% Co spinel phase NCO films are intrinsically the most active. The studies point to a chemical composition dependent OER mechanism: Co‐rich spinel films show instantly high activities, while the more sustainable Ni‐rich rock‐salt films require extended activation to increase the ECSA and OER performance. The results highlight the added value of working with model systems to disclose structure‐performance mechanisms. [ABSTRACT FROM AUTHOR]

To combat with energy crisis considering clean energy, oxygen evolution reaction (OER) is crucial to implement electrolytic hydrogen fuel production in real life. Here, straightforward chemical synthesis pathways are followed to prepare cobalt tetraoxide nanoparticles (Co3O4NPs) in an alkaline OER process using poly[(2‐methacryloyloxy)ethyl]trimethylammonium chloride (Co3O4NPs@PMTC) as support to prevent aggregation. In material characterization, the X‐ray diffraction (XRD) pattern confirms the crystallinity of the synthesized Co3O4NPs@PMTC, and Raman spectroscopy indicates that the Co3O4NPs contain cubic close‐packed oxides. The morphological analysis reveals the wrinkle‐like disruption which is distributed evenly owing to the folded nanosheet arrays. Energy‐dispersive X‐ray spectroscopy indicates the presence of a significant number of cobalt atoms in the Co3O4NPs, and elemental mapping analysis demonstrates the composition of the NPs. At a current density of 10 mA cm−2, oxygen is emitted at 1.67 V delivering an overpotential of 440 mV. This unique structure of Co3O4NPs@PMTC provides beneficial functions that are responsible for a large number of active sites and the rapid release of oxygen gas with long‐term stability. Through kinetic study, we found a Tafel slope of 48.9 mV dec−1 which proves the catalytic behavior of Co3O4NPs@PMTC is promising toward the OER process. [ABSTRACT FROM AUTHOR]

[Display omitted] Properly design and fabricate capable electrocatalysts with 3D hierarchical hollow framework to realize cost-effective and efficacious overall water splitting (OWS) are particularly meaningful for the large-scale arrangement of pivotal energy technology. In this study, P-doped NiCo 2 O 4 nanoparticles encapsulated in N -doped carbon hierarchical hollow nanoflowers (P-NiCo 2 O 4 @NCHHNFs) were constructed using the hydrothermal-pyrolysis-phosphorization approach. This fascinating architecture can not merely serve as a conductive pathway for electron transfer, but at the same time effectively inhibited the aggregation and corrosion of the NiCo 2 O 4 nanoparticles. Additionally, the P doping not only regulates electronic structure configuration to boost the intrinsic activity of the catalyst, but also enhance electrochemical surface areas to reveal more accessible active sites. Attributing to these characteristics, the as-prepared P-NiCo 2 O 4 @NCHHNFs exhibit preeminent electrocatalytic performance with low overpotentials of 283 mV and 162 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) (at 10 mA cm−2), respectively. Specifically, by using the P-NiCo 2 O 4 @NCHHNFs as bifunctional catalysts, a low potential of 1.56 V (at 10 mA cm−2) is sufficient to drive overall water splitting with splendid durability. This study proposed an innovative strategy for the conceiving and fabricating high-performance catalysts via heteroatom-doping. [ABSTRACT FROM AUTHOR]

Utilizing strain-induced polarization to amplify the performance of photo-catalytic water-splitting systems has garnered significant attention in view of clean H 2 evolution with no environmental footprint. However, achieving efficient charge separation, high underwater suspension efficiency, and sustained cyclic stability remains a persistent challenge. In this study, we employed a classic low-temperature ball milling technique to synthesize rhombohedral bismuth sodium titanate phase B 0.5 Na 0.5 TiO 3 as a matrix material. One-step superimposed reduced graphene oxide with cobalt oxide loading RGO-Co 3 O 4 is used as reinforcement. The cobalt oxide (Co 3 O 4) is expected to speed up classically slow OER reaction. The addition of reinforcement lowers the band gap of our material and makes it more visible light active to optimize full spectrum absorption. We report a 14.79% increase in H 2 evolution with the addition of reinforcement and optimal H 2 evolution was achieved with 5% RGO-Co 3 O 4 (517 μmol/g-h). After the introduction of simultaneous photo and piezoelectric potential by using an ultrasonicator, H 2 evolution is much enhanced 109 μmol/g-h surpassing piezo catalysis 66 μmol/g-h and photo catalysis 64 μmol/g-h. Herein, we also explore renewable alternatives using manure and seawater revealing improved H 2 evolution that is 1.8% and 50.4% respectively. Additionally, the piezo-photo catalyst demonstrates remarkable performance without a sacrificial agent further highlighting its exceptional potential. Moreover, we also uncover the role of Co 3 O 4 as a co-catalyst and RGO as a promoter in direct and indirect z-schemes for water splitting. This work provides insight into harnessing and designing ingenious composites for efficient and stable piezo-photo catalysts for efficient and stable water-splitting systems. [Display omitted] • A novel metal-free BNT/RGO-Co 3 O 4 z-scheme composite piezo-photo catalyst was fabricated successfully. • The same piezo-photo catalyst was used for renewable mediums such as seawater and manure. • The catalyst demonstrates a direct z-scheme for the higher concentration of co-catalyst with no need for promoter. • The inclusion of BNT in the piezo-photo catalyst is responsible for both direct and indirect bands in all composite variants. [ABSTRACT FROM AUTHOR]

Active and stable electrocatalysts with low precious metal loading is essential for the widespread application of proton-exchange water electrolyzers. Construction of core-shell structure offers the possibility to achieve high catalytic activity and good stability, and simultaneously to reduce the precious-metal loading. Here, Co 3 O 4 -core IrO x -shell nanoparticles (Co 3 O 4 @IrO x) are synthesized by immersing the solvothermal synthesized Co 3 O 4 in alkaline IrCl 3 aqueous solution, followed by annealing at 350 °C for 2 h. The Co 3 O 4 @IrO x -10, which exhibits the highest oxygen evolution reaction (OER) activity when supported on carbon paper, are 9.76 nm in average diameter, and the surface IrO x layer is about 0.97 nm. Only 337 mV overpotentials are required to reach the 10 mA cm−2 OER current densities in 0.1 M HClO 4 for the Co 3 O 4 @IrO x -10, with the mass activity reaches 1.44 A mg−1 Ir at 370 mV overpotentials. The high OER activity is originated from the increased number of active sites and more facile kinetics, demonstrated by the lower charge transfer resistance, lower activation energy and lower Tafel slope values. The optimized adsorption energy of OH* intermediates caused by the electronic interaction between the Co 3 O 4 core and the IrO x shell facilitates the OER kinetics. The Co 3 O 4 @IrO x -10 supported on carbon paper is stable towards the long-term OER in acid, and the IrO x shell layer can effectively protect the Co 3 O 4 core. The Co 3 O 4 @IrO x -10 are promising candidates as the low precious metal electrocatalysts for OER in acid. • The Co 3 O 4 @IrO x -y core-shell nanoparticles are synthesized successfully. • The core-shell structure enhanced the activity and stability of the catalyst. • The core-shell structure significantly reduced the amount of IrO x addition. • The electron interaction between Co 3 O 4 and IrO x optimizes the adsorption energy of OH* intermediates. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogen production and supercapacitor technologies have positive impacts on the environment, promoting the production and utilization of clean and renewable energy sources, thus facilitating the reduction of greenhouse gas emissions. Among them, cobalt oxide (Co 3 O 4) has emerged as an ideal choice for electrode materials in these technologies due to its low toxicity, affordability, and significant theoretical capacity. Nevertheless, practical applications are restricted by its low conductivity and sluggish reaction kinetics. Addressing these challenges, this study introduces a pioneering approach: the synthesis of oxygen vacancy-modified Co 3 O 4 /Co/NC small-sized nanoflower composite, which combines the advantages of abundant oxygen vacancies, small size effects, and nitrogen-doped porous carbon. The optimized Co 3 O 4 /Co/NC small-sized nanoflower exhibits high porosity and excellent conductivity, providing numerous active sites and effectively enhancing the ion and electron transport rates. As a consequence, optimized Co 3 O 4 /Co/NC shows a low Tafel slope and overpotential, highlighting its potential for catalytic application. Moreover, as an electrode for supercapacitors, optimized Co 3 O 4 /Co/NC demonstrates excellent long-term stability, maintaining 94.7% of its capacitance even after 5000 charge-discharge cycles. Additionally, it showed a significant specific capacity of 251.4 mAh g−1 when tested at 1 A g−1. In addition to addressing the pressing challenges associated with traditional Co 3 O 4 electrodes, this work opens up exciting avenues for designing and fabricating transition metal oxide-based materials with unprecedented electrochemical performance. This research addresses performance issues with cobalt oxide as an electrode material for capacitors and green hydrogen generation. Innovative methods involving nitrogen doping and the introduction of oxygen vacancies were employed to produce Co 3 O 4 /Co/NC-2 nanosheets with high porosity and a large surface area. These enhancements facilitate faster electrolyte ion diffusion, provide more active sites, and improve electrical conductivity. Nitrogen doping enhances charge transfer rates, while oxygen vacancies offer additional catalytic sites. [Display omitted] • Nitrogen doping and oxygen vacancies enhance the conductivity and reaction rate of cobalt oxide. • Nanoflowers prepared using freeze-drying technology exhibit high porosity, facilitating the diffusion of electrolytes. • This material can be applied in the fields of green catalysis and energy storage. [ABSTRACT FROM AUTHOR]

Nanostructure of copper doped cobalt oxide nanoparticles were synthesized by microwave irradiation assisted method. The prepared nanoparticles were further characterized by using powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and UV-Vis spectroscopy. The crystalline nature of the nanoparticles is evident from the presence of peaks in the powder X-ray diffraction pattern. The average crystallite size is found to be 20 nm calculated using Debye-Scherer formula. The different functional groups and molecular vibrations are conformed by Fourier transform infrared spectroscopy. The morphological survey of prepared nanoparticles is done by using SEM at 200 nm and 1 µm, respectively. From the micrograph we can confirm the needlelike morphology. The optical properties of nanoparticles were characterized by UV-Vis-NIR spectroscopy. From the tauc plot it is found to be 4.52 eV for indirect transition. [ABSTRACT FROM AUTHOR]

Recently, hybrid capacitive deionization (HCDI) has been a promising desalination technology because of its low cost and effective ion removal ability. The electrode material is an important factor to affect to desalination capacity of HCDI technology. In this study, the nanocomposite electrodes were fabricated successfully based on activated carbon and reduced-graphene oxide/cobalt oxide (rGO-Co3O4) and polymeric binders which were used as cathode electrodes for Hybrid capacitive deionization (HCDI) technology. The effect of polyvinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) polymeric binders and the amount of rGO-Co3O4 on characteristic as well as specific capacitance of the nanocomposite electrodes were investigated. The nanocomposite electrode combined hydrophilic binder of PVA-based and 50 % rGO-Co3O4 has a specific capacitance of 15.3 mg/g in 200 ppm NaCl solution after 25 min at 1.2 V, which is 1.67 times higher than that of the AC-based electrode. [ABSTRACT FROM AUTHOR]

The paper presents the results of cobalt corrosion tests in air at different temperature and humidity values. It was demonstrated that corrosion losses in cobalt at temperatures of 20 and 30 °C and relative humidity of 70, 80, and 95% are insignificant. However, the rate of cobalt corrosion sharply increases at an air temperature of 50 °C, especially at 95% relative humidity. A conclusion about the intensity of the cobalt corrosion processes under these conditions can also be derived from the sample appearance: after testing at 50 °C and 70% humidity, the samples turn black, while at 50 °C and 95% humidity they become covered with black, oily, and easily crumbling flakes, which represent the products of cobalt corrosion. It was found that corrosion film formed on the cobalt surface consists of the eutectic Co–CoO mixture of variable composition and CoO·Co(OH)2·H2O complex oxide. At increased corrosion test temperatures, the surface film of hydrated cobalt oxide becomes thicker, develops microcracks, and leads to the formation of cobalt hydroxide flakes, which exhibit weak adhesion to the substrate and crumble. [ABSTRACT FROM AUTHOR]

Detection of volatile organic compounds (VOCs), particularly 2-butanone, has become crucial due to their widespread use and associated risks to human health. In this study, we present a novel synthesis method for spinel Co 3 O 4 nanoparticles (NPs) employing a microwave-assisted hydrothermal approach followed by calcination and investigate their efficiency in VOC sensing applications. The Co 3 O 4 NPs exhibit remarkable sensitivity and selectivity towards butanone at relatively low operating temperatures. VOC-sensing experiments reveal an optimal operating temperature of 250 ° C , showcasing an advantage over existing sensors. Notably, the sensor exhibits high selectivity for butanone, with signal values 1.6–4.5 times higher than those for other VOCs, including acetaldehyde, ethanol, isopropanol, methanol, acetone, m-xylene, toluene, and benzene. Additionally, the Co 3 O 4 NPs-based sensor demonstrates high sensitivity, detecting concentrations as low as 5 ppm of butanone, with fast response/recovery times of 41/86 s for 200 ppm of butanone and robust long-term stability. These findings underscore the potential of Co 3 O 4 NPs as promising candidates for low-temperature butanone detection, which is essential for environmental and human health monitoring purposes. [Display omitted] [ABSTRACT FROM AUTHOR]

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The monitoring of antioxidants is crucial to prevent damage caused by reactive oxygen species (ROS). In this study, we introduce an innovative electrochemical sensor tailored for detecting riboflavin (RF), a powerful antioxidant. The sensor was developed by modifying a gold electrode (AuE) with cobalt oxide (Co3O4) and reduced graphene oxide (rGO). The resulting nanocomposite‐modified electrode (AuE/Co3O4‐rGO) exhibited a substantial surface area of 0.41 cm2 in the redox probe, leading to an enhanced RF peak characterized by remarkably low charge transfer resistance (1.61 KΩ) and a high exchange current density (18.6 μA/cm2). Under optimized conditions, the sensor achieved a limit of detection (LOD) for RF at 1.30 μM, over a concentration range of 6.5–42.2 μM. These results highlight the sensor's potential applicability in real‐world scenarios, including the analysis of milk and pharmaceutical samples. A kinetics study revealed that the electrochemical reaction involving RF is adsorption‐controlled, emphasising the critical role of surface interactions. The modified electrode's interaction with RF significantly influences overall reaction kinetics. These findings were further supported by density functional theory (DFT) calculations and molecular simulations. Our nanocomposite‐modified electrode provides valuable insights into the atomistic interactions governing sensor performance, advancing the field of electrochemical sensing for antioxidants like riboflavin. [ABSTRACT FROM AUTHOR]

A cobalt-loaded magnetic biochar (Co-MBC) catalyst was synthesized to enhance the removal of metronidazole (MNZ). Study explored the performance and mechanism of MNZ degradation by Co-MBC activated permonosulfate (PMS). Results showed that cobalt oxides were effectively deposited onto the biochar surface, new oxygen functional groups were added to the modified biochar, and the presence of the metallic element Co enhanced the efficiency of PMS activation in the composite. More than 90% of MNZ was removed after 60 min with a catalyst dosage of 0.2 g/L and a PS concentration of 1 mM. After four reuses, Co-MBC still showed excellent catalytic performance to degrade over 75% of MNZ. The reaction system performed well even in the presence of inorganic anions and organic macromolecules. However, the degradation rate was inhibited under alkaline conditions. The quenching experiment indicated that •SO4−, •OH, 1O2, and •O2− synergistically degraded MNZ, and that•SO4− played a dominant role. LC-MS was applied to assess intermediate degradation products, in which CO2, H2O, and NO3− were the final degradation products, and potential degradation pathways were suggested. In conclusion, Co-MBC was an efficient and stable catalytic material, and its ability to activate PMS was improved to effectively degrade antibiotics, a typical priority pollutant. [ABSTRACT FROM AUTHOR]

In this study, Co 3 O 4 nanofibers were produced using the solution blow spinning (SBS) method. The investigation focused on studying their structure, morphology, and electrocatalytic properties in relation to the oxygen evolution reaction (OER) in alkaline solution (KOH). Calcination at 600 °C resulted in Co 3 O 4 fibers without the presence of secondary phases (NF600), while calcined fibers at 400 °C showed a Co 3 O 4 –CoO composite phase (NF400), confirmed by XRD. The size of the crystallites, determined through Rietveld refinement analysis of XRD patterns, ranged from 42.6 nm to 56.2 nm for the calcined fibers at 400 °C and 600 °C, respectively, confirming the nanometric scale of the cobalt oxide fibers. Morphological analyses confirmed the production of rough nanofibers with monomodal distribution, with mean diameter of 385 nm for NF600 and 485 nm for NF400. The EDS confirms the presence of the chemical elements of cobalt and oxygen, estimating their abundance in the sample. The XPS analysis showed that the concentration of oxygen vacancies and the presence of species with higher oxidation states (Co3+) were beneficial to improve OER. Nanofibers calcined at 600 °C showed an overpotential of 330 mV at 10 mA cm−2, more efficient Tafel kinetics and low resistance to charge transfer (0.37 Ω) when compared to nanofibers calcined at 400 °C (338 mV). This result demonstrates the competitive catalytic activity of cobalt oxide nanofibers produced by SBS compared to other systems mentioned in the literature. Therefore, this work offers a new perspective on the development of electrocatalysts based on the structure and properties of cobalt oxide electrodes by the SBS method. [ABSTRACT FROM AUTHOR]